The use of chains of preopened plastic bags to form packages is now well known. Such chains of bags are disclosed and claimed in U.S. Pat. No. 3,254,828 entitled FLEXIBLE CONTAINER STRIPS (the Autobag Patent). A commercial version of a machine described and claimed in U.S. Pat. No. 3,965,653 entitled PACKAGING APPARATUS, and in other patents deriving from the applications that resulted in this patent, (the H-100 Patents) has been sold commercially by Automated Packaging Systems, Inc. under the designation H-100. With the very successful H-100 machine, bags of an interconnected chain are sequentially fed one at a time to a load station. Once a bag is positioned in the load station, a product is inserted and bag separation and sealing of the loaded bag is performed to provide a completed package.
A machine described and claimed in U.S. Pat. No. 4,899,520 entitled PACKAGING APPARATUS AND METHOD (the H-200 Patent) functions in a manner similar to the H-100 but has additional capabilities including the ability concurrently to utilize two chains of bags for "double up" packaging.
With the machines of the H-100 and H-200 patents loaded, bags are sealed at sealing stations each through contact with a heater bar which melts a portion of the plastic. During the sealing operation, the weight of a bag's contents and bag separation forces are isolated from the seal by spring-biased grippers which are moved into bag engagement by a clamping sub-assembly that concurrently brings the loaded bag into contact with the heater bar. All of these moving parts can be interfered with by a product that is only partially loaded or a foreign object thereby causing jams which can damage the machine and/or the product or can cause an improper seal which creates an unacceptable package.